Data from several cancer screening studies are being collected and analyzed to gain a better understanding of the impact and consequences of such screening in various population settings, and to develop new techniques for data analysis. Section staff are involved in various aspects of these studies, including design, monitoring, and data analysis. The data base from the HIP breast cancer screening trial was used to address several scientific and modeling issues. Issues under investigation included the magnitude and duration of benefit, age-specific effectiveness, and application to model development. Data from the NCI sponsored lung cancer screening trials were analyzed. Investigations included assessment of incidence and mortality information. Monitoring continues of a trial to evaluate testing for blood in the stool for the early detection of colorectal cancer. Staff are also involved in several observational studies of screening procedures. In collaboration with investigators from the Centocor Company, the value of using the CA125 assay as a test for the early detection of ovarian cancer is being studied. Preliminary results indicate that the test may have a reasonable specificity and predictive value in post menopausal women. Study designs are under consideration to assess sensitivity and evaluate the impact of screening on ovarian cancer mortality. Evaluation of screening for neuroblastoma in infants is also being addressed in conjunction with investigators at the University of Minnesota. Staff are assisting with the design of a controlled study to assess the measurement of urinary catecholamine metabolites VMA and HVA as screening tests for this tumor. An additional collaborative effort involves examination of study design and data analysis approaches for evaluating screening for stomach cancer in Shandong Province, People's Republic of China.